Photoperiodism is a quality of most plants that controls a plant's response to changes in light. Diurnal, or day and night, changes in light are cues to the plant to undertake certain responses, and in many plants the length of day or night is itself a cue. These responses include germination of seeds, start of flowering, and smaller, more granular changes like nighttime processes that plants undertake when not actively photosynthesizing.
Indoor horticulture has been able to reproduce and in some cases enhance natural processes to permit plants to be grown without natural sunlight, or, in some cases, with supplemental light in addition to natural sunlight. Current methods of providing horticultural lighting are similar to those used in other lighting applications, usually involving a single incandescent bulb or multiple LED chips to provide a varying spectrum of light and employing a simple analog on-off switch. None of the current methods include offset timing for different spectra. Such methods do not adequately simulate natural sunrise and sunset conditions that some plants require to switch between daytime and nighttime activities. Such methods also do not allow enhanced photoperiodic responses that can be obtained by offset timing for specific spectra.
Plants use a photosensitive pigment to detect light. One of these, phytochrome detects light in the red and far red spectrum and affects plant signals to “wake” or “sleep.” Different important biological processes occur in plants during these times. In addition to the time of day, many plants track the length of days with phytochrome and related systems; this allows, for example, a plant to know when the days are getting shorter in the fall, signaling the best time to convert from producing vegetative tissues to producing flowering tissues.
Reference to, and discussion of, the foregoing background is not presented as prior art and is respectfully submitted that none of the above-indicated patents and patent applications disclose, teach, suggest, show, or otherwise render obvious, either singly or when considered in combination, the invention described and claimed herein.
For the foregoing reasons, there is a need for a lighting system that provides offset timing for different light sources and spectra.